The short version of Cyclic heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-03-25. Anything still debated is marked as such rather than presented as settled.
The molecular backbone consists of seven amino acid residues joined into a ring through a disulfide bridge. This cyclic conformation is critical for receptor binding. The sequence includes an acetylated N-terminus and an amidated C-terminus, modifications that improve resistance to enzymatic breakdown. One residue is in the D-configuration, a feature that further stabilizes the peptide against protease activity. Together, the ring structure and specific stereochemistry determine selectivity among melanocortin receptor subtypes.
Across literature and commercial listings, the substance appears under several names, including bremelanotide, PT-141, and various brand designations. A CAS registry number provides a unique identifier for the compound, aiding retrieval from chemical databases. Synonym lists may also contain early development codes and descriptive chemical names. When consulting sources, researchers need to confirm that the cited names refer to the same molecular structure to avoid confusion. Naming consistency matters especially when comparing analytical data across publications.
Handling procedures emphasize minimizing moisture uptake, since the dried solid is hygroscopic and can draw water when warmed to room temperature before a vial is opened. Laboratories record lot number, purity, counter-ion content, and residual solvent data supplied by the producer. Impurity profiles are compared run to run, and any shift in retention time or peak shape prompts re-verification against a reference standard. Certificates of analysis are treated as claims to be checked rather than accepted at face value.
Identity and purity testing for this peptide typically relies on reversed-phase high-performance liquid chromatography with ultraviolet detection, reported as area-percent purity. Mass spectrometry, usually in tandem mode, confirms molecular mass and supports quantification in biological matrices. Sequence confirmation may use peptide mapping after enzymatic digestion, while nuclear magnetic resonance and circular dichroism supply supplementary structural detail. No single technique establishes identity alone, so laboratories compare retention time, mass, and fragment pattern against a verified reference standard.
The lactam ring that closes the peptide backbone improves resistance to exopeptidase attack, but the molecule stays susceptible to hydrolysis and oxidation once dissolved. Degradation accelerates with temperature, extreme pH, and light exposure, and repeated freeze-thaw cycles promote aggregation and material loss. Lyophilized powder held desiccated at or below minus twenty degrees Celsius is the common way to keep reference material. Reconstituted solutions are generally kept cold and used within a short window because their stability is far lower than that of the dry solid.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Cyclic peptide | Melanocortin receptor agonist family |
| Molecular weight | Approximately 1025 Da | Free base form |
| Appearance | White to off-white powder | Lyophilized product |
| Solubility | Soluble in water | Also dissolves in polar organic solvents |
| Storage temperature | -20 degrees Celsius | Dry and protected from light |
Receptor activation in hypothalamic and limbic circuits is the mechanism most often cited for the observed effects on sexual desire. Signalling through MC4R couples to Gs proteins and raises intracellular cyclic AMP, which in turn modulates dopaminergic tone in reward-related pathways. Because the peptide reaches the central nervous system after subcutaneous administration, peripheral vascular changes are regarded as secondary rather than primary. The precise neural circuits that translate receptor occupancy into behavioural change remain incompletely mapped, and published accounts describe the pathway in general terms rather than as a fully resolved sequence.
Development began with intranasal formulations investigated for erectile dysfunction, but blood pressure elevation limited that route and prompted a switch to subcutaneous delivery. Clinical testing then shifted toward hypoactive sexual desire disorder in premenopausal women, and a subcutaneous product received United States approval in 2019. Later trials examined other populations with mixed results, and questions about effect size, durability and patient selection remain open in the peer-reviewed literature. Research interest continues in parallel with the broader melanocortin field, where several synthetic analogues are studied together.
Clinical research typically uses randomised, double-blind, placebo-controlled designs. The most common primary endpoint is the desire domain score of the Female Sexual Function Index, sometimes paired with a distress measure. Secondary outcomes include arousal, satisfaction, and event-based counts of satisfying sexual episodes. Across trials, average improvements are modest and individual responses vary widely. Whether benefits persist beyond a few months, and whether they depend on baseline hormone status, remain open questions rather than settled findings.
Melanocortin receptors form a family of five G-protein-coupled receptors designated MC1 through MC5. Bremelanotide binds most strongly at MC4R and MC1R, with weaker activity reported at MC3R and MC5R. MC4R is expressed in hypothalamic nuclei that coordinate energy balance and aspects of sexual behaviour. The prevailing interpretation is that central MC4R activation, rather than peripheral vascular effects alone, drives the reported changes in desire. This account remains partly inferential, since direct receptor-level measurement in living humans is not practical.
=== Nervous system === Prenatal exposure of BaP in rats is known to affect learning and memory in rodent models. Pregnant rats eating BaP were shown to negatively affect the brain function in the late life of their offspring. At a time when synapses are first formed and adjusted in strength by activity, BaP diminished NMDA receptor-dependent nerve cell activity measured as mRNA expression of the NMDA NR2B receptor subunit.
exocytosis Any active transport process by which a substance is secreted from or transported out of a cell, crossing the plasma membrane from the interior of the cell into the extracellular space, especially that which occurs by the fusion of the membrane surrounding a secretory vesicle with the larger cell membrane. This fusion causes the intra-vesicular space to merge with the extracellular fluid, releasing the vesicle's contents on the exterior side of the cell without exposing them to the hydrophobic space between the lipid bilayer. More narrowly the term may refer in particular to the bulk transport of a large amount of molecules out of the cell all at once, often metabolites or hormones which are too large and polar to passively diffuse across the membrane themselves. The reverse process, whereby materials are invaginated into the cell, is known as endocytosis.
On the other hand, hydrophobic (M, I, L, V) and aromatic amino acids (F, Y, W) as well as cysteine, arginine and asparagine are heavily under-represented in LCRs. Very similar trends for amino acids with a high (G, A, P, S, Q) and low (M, V, L, I, W, F, R, C) occurrence within LCRs have been observed in eukaryotes as well. This observed pattern of certain amino acids being over-represented (enriched for) or under-represented in LCRs could be partially explained by the energy cost for synthesis or metabolism of each of the amino acids. Another possible explanation, which does not exclude the previous explanation of energy cost could be the reactivity of certain amino acids. For example, Cysteine is a very reactive amino acid that would not be tolerated in high numbers within a small region of a protein. Similarly, extremely hydrophobic regions can form non-specific protein–protein interactions among themselves and with other moderately hydrophobic regions in mammalian cells. Thus, their presence may disturb the balance of protein-protein interaction networks within the cell, especially if the carrier proteins are highly expressed. A third explanation may be based on micro-evolutionary forces and, more specifically, on the bias of DNA polymerase slippage for certain di- tri- or tetra-nucleotides .
A week later, after meeting Heseltine, the constituency officers issued another letter saying that they regretted how their reply had been construed as criticism. Then came Howe's resignation speech in the Commons on 13 November, in which he launched a strong attack on Thatcher; next morning Heseltine announced his candidacy for the leadership, saying that over 100 MPs had asked him to stand and that he was better placed than Thatcher to lead the Tories to a fourth election victory. During the subsequent leadership election on 20 November, he polled 152 votes (40.9%) in the first round of voting by Conservative MPs, enough to prevent an outright Thatcher victory. (The rules required an incumbent leader to obtain a majority of at least 15% on a first ballot; Thatcher polled 204 votes, equal to 54.8%). Heseltine was thought by many pundits to be on course to beat her in the second ballot as many Conservative MPs were now rumoured to be ready to switch support from Thatcher and only 27 would have had to have done so to give Heseltine the overall majority he would need in the second ballot. With lukewarm support from her Cabinet, most of whom had told her that she could not win and faced with the bitter prospect of a Heseltine premiership, Thatcher withdrew from the contest and announced her resignation on the morning of 22 November, although she continued to serve as prime minister until a new party leader had been chosen.
Pea proteins have been criticized for their potentially bitter, metallic taste, caused by compounds called saponins. Depending on the method of processing, pea protein can have an undesirably gritty texture. Depending on the method of processing, some pea proteins can contain high levels of anti-nutritional properties such as phytates, lectins, and trypsin inhibitors, which have negative side effects. Trypsin inhibitors decrease the digestion of the protein. Lectins can impede the uptake of glucose, decrease nutrient transport, and create damage to the mucosal layer of the intestines by binding to carbohydrate molecules. Phytates affect the bioavailability and digestibility of the protein by forming complexes with essential dietary minerals such as iron, zinc, and calcium, affecting their absorption.
Sources: en.wikipedia.org
I was holding excerpts (photocopies were not so accessible then) from the author's certificate USSR № 1247973 to which I have referred in all my works on the Orbitrap™ analyzer since then." Alexander Makarov's effort in commercializing Orbitrap analyzer at the end of the 1990s required a number of innovations such as image current detection, C-trap for ion injection, and other technology improvements which resulted in the commercial introduction of this analyzer by Thermo Fisher Scientific as a part of the hybrid LTQ Orbitrap instrument in 2005.
==== GAR transformylase ==== PurN GAR transformylase is found in eukaryotes and prokaryotes. However, a second GAR transformylase, PurT GAR transformylase has been identified in E. coli. While the two enzymes have no sequence conservation and require different formyl donors, the specific activity and Km for GAR are the same in both PurT and PurN GAR transformylase.
== General references == Acheson, D. J. (1990), Elementary Fluid Dynamics, Oxford Applied Mathematics and Computing Science Series, Oxford University Press, ISBN 978-0-19-859679-0 Batchelor, G. K. (1967), An Introduction to Fluid Dynamics, Cambridge University Press, ISBN 978-0-521-66396-0 Currie, I. G. (1974), Fundamental Mechanics of Fluids, McGraw-Hill, ISBN 978-0-07-015000-3 V. Girault and P. A. Raviart. Finite Element Methods for Navier–Stokes Equations: Theory and Algorithms. Springer Series in Computational Mathematics. Springer-Verlag, 1986 Landau, L. D.; Lifshitz, E. M. (1987), Fluid mechanics, vol. Course of Theoretical Physics Volume 6 (2nd revised ed.), Pergamon Press, ISBN 978-0-08-033932-0, OCLC 15017127 Polyanin, A. D.; Kutepov, A. M.; Vyazmin, A. V.; Kazenin, D. A. (2002), Hydrodynamics, Mass and Heat Transfer in Chemical Engineering, Taylor & Francis, London, ISBN 978-0-415-27237-7 Rhyming, Inge L. (1991), Dynamique des fluides, Presses polytechniques et universitaires romandes Smits, Alexander J. (2014), A Physical Introduction to Fluid Mechanics, Wiley, ISBN 0-47-1253499 Temam, Roger (1984): Navier–Stokes Equations: Theory and Numerical Analysis, ACM Chelsea Publishing, ISBN 978-0-8218-2737-6 Milne-Thomson, L.M., C.B.E (1962), Theoretical Hydrodynamics, Macmillan & Company Limited Tartar, L (2006), An Introduction to Navier Stokes Equation and Oceanography, Springer ISBN 3-540-35743-2 Birkhoff, Garrett (1960), Hydrodynamics, Princeton University Press Campos, D.
==== Branding irons ==== Freeze brands are distinct from hot branding irons, which are generally made from steel or cast iron. Freeze brands at their working temperature possess a smaller difference in temperature from 25 °C than hot brands (−72 °C to −196 °C vs +500 °C). They must therefore be applied for much longer durations—up to 1 minute, compared to 3–5 seconds for hot branding. Further, the rapid removal of heat fundamentally differs from the sudden addition of heat, both in its physiological effects and the time required to achieve a given change in temperature. To compensate for these disadvantages the thermal conductivity of the brand is far more important in freeze branding than it is in hot branding. Freeze brands are occasionally made from pure copper but are more often made of a cupronickel alloy. This alloy was selected to exploit copper's high thermal conductivity (only diamond and silver are better heat conductors) and nickel's ability to extend copper's high thermal conductivity into cryogenic temperature regimes. Maximum thermal conductivity is desirable because it directly controls how long the supercooled iron must be pressed to the animal's skin. For this reason, steel, brass, bronze and aluminum cryogenic brands are no longer widely used. Commercial freeze brands generally have a stamp on the stem end indicating what shape of the brand will be produced. This allows the user to select the right brand from the coolant bath without lifting each out to inspect its face.
Sources: en.wikipedia.org
It belongs to the melanocortin receptor agonist family of peptides. Its cyclic structure distinguishes it from linear peptides and shapes its receptor binding profile.
It emerged from research on melanotan II. Investigators exploring derivatives observed distinct pharmacological features related to sexual function.
Common names include bremelanotide and PT-141. Chemical databases may also list early development codes and descriptive names.
Chemical degradation such as hydrolysis and oxidation proceeds more slowly as temperature falls. Cold storage also limits microbial growth in reconstituted material. Repeated warming should be avoided because thermal cycling stresses the peptide.